The aim is to determine how the action potential causes muscle contraction. Two sub-microscopic intracellular systems of vesicles and channels are important in linking the two events: The T-system and the sarcoplasmic reticulum. The voltage-clamp technique will be used to investigate electrical excitation in the T-system, as well as electrical signs of sarcoplasmic reticulum/T-system interaction. Experiments will be designed to study the role of non-ionic gating currents in the regulation of contraction. BIBLIOGRAPHIC REFERENCES: Adrian, R.H. & Almers, W. (1976). Charge movement in the membrane of striated muscle. J. Physiol. Lond. 254: 339-361. Almers, W. & Best, P.M. (l976). Effects of tetracaine on contraction and "gating currents" in frog skeletal muscle. Biophys. J. 16: 152a.